> -----Original Message-----
> From: Andreas Färber [mailto:afaer...@suse.de]
> Sent: Monday, June 10, 2013 5:43 PM
> To: Bhushan Bharat-R65777
> Cc: qemu-...@nongnu.org; qemu-devel@nongnu.org; ag...@suse.de; Wood Scott-
> B07421; Bhushan Bharat-R65777
> Subject: Re: [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for
> target_bit above 61
>
> Am 10.06.2013 09:55, schrieb Bharat Bhushan:
> > QEMU timer supports a maximum timer of INT64_MAX. So starting timer
> > only for time which is calculated using target_bit < 62 and
> > deactivate/stop timer if the target bit is above 61.
> >
> > This patch also fix the time calculation from target_bit.
> > The code was doing (1 << (target_bit + 1)) while this should be (1ULL
> > << (target_bit + 1)).
> >
> > Signed-off-by: Bharat Bhushan <bharat.bhus...@freescale.com>
> > ---
> > v1->v2
> > - Added "booke: timer:" in patch subject
> >
> > hw/ppc/ppc_booke.c | 8 +++++++-
> > 1 files changed, 7 insertions(+), 1 deletions(-)
> >
> > diff --git a/hw/ppc/ppc_booke.c b/hw/ppc/ppc_booke.c index
> > e41b036..f4eda15 100644
> > --- a/hw/ppc/ppc_booke.c
> > +++ b/hw/ppc/ppc_booke.c
> > @@ -133,9 +133,15 @@ static void booke_update_fixed_timer(CPUPPCState
> *env,
> > ppc_tb_t *tb_env = env->tb_env;
> > uint64_t lapse;
> > uint64_t tb;
> > - uint64_t period = 1 << (target_bit + 1);
> > + uint64_t period;
> > uint64_t now;
> >
> > + /* Deactivate timer for target_bit > 61 */
> > + if (target_bit > 61)
> > + return;
>
> Braces missing and trailing whitespace after return.
Ok, will correct
>
> So IIUC we can only allow 63 bits due to signedness, thus a maximum of
> (1 << 62), thus target_bit <= 61.
>
> Any chance at least the comment can be worded to explain that any better?
> Maybe
> also use (target-bit + 1 >= 63) or period > INT64_MAX as condition?
How about this:
/* QEMU timer supports a maximum timer of INT64_MAX (0x7fffffff_ffffffff).
* Run booke fit/wdog timer when
* ((1ULL << target_bit + 1) < 0x40000000_00000000), i.e target_bit = 61.
* Also the time with this maximum target_bit (with current range of
* CPU frequency PowerPC supports) will be many many years. So it is
* pretty safe to stop the timer above this threshold. */
>
> Best regards,
> Andreas
>
> > +
> > + period = 1ULL << (target_bit + 1);
> > +
> > now = qemu_get_clock_ns(vm_clock);
> > tb = cpu_ppc_get_tb(tb_env, now, tb_env->tb_offset);
> >
> >
>
>
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